alleryWhich of these is NOT possible for the offspring of a TT × tt cross?
AAll TT homozygous tall
BAll Tt heterozygous tall
CGenotype matches one parent and not the other
DPhenotype tall in 100 percent of cases
Answer & Solution
Correct answer: A. All TT homozygous tall
1. The TT parent contributes only T gametes.
2. The tt parent contributes only t gametes.
3. Every fertilisation gives a Tt zygote.
4. So every F₁ offspring is heterozygous Tt and shows the dominant tall phenotype.
5. No offspring is homozygous TT because no t-free × t-free combination is possible.
6. Hence option B (all TT homozygous tall) is impossible from this cross.
_Source: syllabus Science Ch 9 'Heredity' (learncbse.in extract)_
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